The security problem of power battery is a factor effecting the development of power battery, increasing the safety protective design of a power battery system to the maximum extent always is the direction of people's efforts. The fuse function of the existing power battery system is provided inside a power management system or a battery module, the electrical connection between mono-batteries most uses an electrical connection sheet of metal, but the electrical connection between mono-batteries are not provided with the fuse function; if increasing the fuse function in the electrical connection between mono-batteries, when the battery module fails and generates a large current which is hazardous, the large current flows through the electrical connection sheet which is between the mono-batteries and makes the electrical connection sheet fused and form a fracturing slit, when the fracturing slit is narrower, the phenomenon of electrical arc easily occurs, if the electrical arc is not extinct in time, the electrical spark generated by the electrical arc may damage the other parts of the battery module and the mono-batteries, and even fire explosion may be caused if the electrical spark is serious.